Fatal error: require_once(): Failed opening required
try chdir(dirname(__FILE__)) this sets the relative path to the path of the file.So C:\XAMPP\htdocs\wapp\ becomes your "root directory" and therefore config.inc.php is the same as C:\XAMPP\htdocs\wapp\config.inc.php. If this still doesn't to the trick check your file paths
Edit:
You have to traverse there. Check the relative root of the project (getcwd()). I assume its C:\XAMPP\htdocs\wapp\ you have to change your require to this:
require_once ('../conf/conf.inc.php') the .. make you go up one directory
OK just do this:
require_once("../conf/conf.inc.php");